Electrical conductivity measurements were performed for liquid immiscible alloys in a wide temperature range under ambient pressures of argon gas (up to 50 MPa). The electrical conductivity shows the same behaviour as for binary liquid alloys during the mixing - demixing process. It was revealed that variation in the Se-to-Te ratio at a constant content of Tl changes the properties of coexisting liquids and affects the temperature of phase separation. The results are analysed in comparison with available data for binary immiscible Tl - Se and Tl - Te system alloys and the possible influence of the ion subsystem on the formation of the critical point parameters is discussed.